Find power of antenna from emf on coil
I want to find power of the electromagnetic waves generated from a welding cable. I built my own coil antenna that is 6.5 inches in diameter (circular) with 50 turns and hooked up the ends to a digital...
View ArticleWhy is there a voltage drop across an impedance?
Firstly, there are lots of ways to word the definition of voltage, but the one that intuitively makes the most sense to me is as follows: "One volt is when: The difference in (electrical potential...
View ArticleShear stress Difficulty
Hi all, I'm having problems with visualising shearforce for a body.Let us take a rectangular prism and fix one of its ends.Let the other end be subjected to a tensile force T Newtons.The normal stress...
View ArticleFriction with a Magnetic Bearing System?
One question that I have been thinking about for a while is if you were to use magnetic bearings (no physical friction) for a type of motor and put energy into it by spinning it and slow it down with...
View ArticleHow do we pick where to set electric potential equal to zero?
Sometimes we set potential to equal zero at infinity, other times at the origin. What's the general rule of thumb here-how do I know which to choose when doing a problem?
View ArticleWhy does the E-field of radiation vary with inverse distance?
Feynman_Lectures_on_Physics_Volume_1_Chapter_28 In 28-2 Radiation Feynman starts talking about the third term of Eq. 28.3 and why that it varies with the inverse of the distance. On page 28-4 he says...
View ArticleStick and waves
Hello. I have got question. We have stick (its diameter is much smaller than its length). When you hit it with a hammer into a corner, some waves will spread, it is clear. However, how do they look?...
View ArticleMaxwell Stress Tensor in the absence of a magnetic field
I'm having some trouble calculating the stress tensor in the case of a static electric field without a magnetic field. Following the derivation on Wikipedia, 1. Start with Lorentz force:...
View ArticleWhy do tanks get hot when you fill them from higher pressure tanks?
I'm a scuba diver - diving since the 1960's. For more years than I'd like to admit, I've wondered why tanks get hot when you fill them from other high pressure tanks. I've seen it happen with "empty"...
View ArticleUse of tensors for dielectric permittivity and magnetic permeability
Hello! In the study of electric and magnetic fields, two equations are called the constitutive relations of the medium (the vacuum, for example): [itex]\mathbf{D} = \mathbf{\epsilon} \cdot \mathbf{E}\\...
View Articlethermodynamics coordinate
i don't really understand which quantities are thermodinamic coordinates and which are not. and what makes work and heat are not thermodinamic coordinates but temperature, volume, etc are thermodinamic...
View Articlesledge hammer physics, impact momentum
I need to find reasonable numbers for acceleration of a sledge hammer when striking a mass of rubber? A strong man can raise the hammer to 8 ft, then brings it down hard. What is reasonable velocity of...
View ArticlePutting a simple momentum equation into words
Check the accuracy of my wording for these first two equations, then, if you could, try to explain the last equation for me. Ʃ F = dp/dt "The total net force acting on a particle is equal to the rate...
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Centripetal Force and Uniform Circular Acceleration
I am in need for some help for a lab report. The issue has happened because there is a lab of 20 students that is being led by a recently retired NASA physicist trying to lead a team of graduate...
View ArticleHow do you calculate the amount of torque you need to pull an object?
HI guys, I am trying to build a pulley with a gear box. So I want my pulley, which is operate by a 3V DC motor with max speed of 8300 RPM. I think the size of the output shaft is 3mm Ok, so Can someone...
View ArticleWhy is the Hamiltonian constructed from the Lagrangian?
I understand how to use Hamiltonian mechanics, but I never understood why you construct the Hamilitonian by first constructing the Langrangian, and then performing a Legendre transform on it. Why can't...
View Articlekinematic questions(velocity of 2 contact points)
in the picture below http://tinypic.com/view.php?pic=9riq9l&s=6 if we know the angular velocity of the gear on the left, as well as their current distance from contact point, what can we say about...
View Articlecentre of gravity of line
what is the centre of gravity of an arc(as opposed to sector) and that of the periphery of triangle(not the area of the triangle)? I'm supposed to use it for calculating blank diameter before drawing...
View ArticleMeaning of Sommerfeld radiation conditions
Hello! Promising that I will not make other new questions in the next days :smile:, I have a doubt about the meaning of a pair of expressions. Sommerfeld's conditions for an electromagnetic field...
View ArticleDuring a phase transition, what is the nature of the material?
As a material is heated, it increases in temperature until it enters a phase transition. During the transition, added heat does not increase the temperature. As this heat is being added, what is the...
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